FIG. 1 illustrates an exemplary standard control configuration for a turbine control system. At the core of the control are three identical control processors, labelled &lt;R&gt;, &lt;S&gt; and &lt;T&gt;, providing triple redundant controls. All critical control algorithms, turbine sequencing, and primary protective functions are handled by these processors. The processors also gather data and generate alarms.
The three control processors accept input from various arrangements of redundant turbine and generator sensors. Data from some sensors is brought into all three control processors, and some data is divided among the control processors. The divided data can be exchanged on the voter link so that each control processor knows all sensor data. Voted sensor values are computed by each of the control processors, producing values that are used in control and sequencing algorithms for required control actions.
Stress calculations have been used in turbine monitoring and control applications. Conventionally, stress algorithms were very complex, requiring programming in separate software. This software was not easily changeable nor viewable. Moreover, a large array of constants of high resolution were required. Still further, due to the size and complexity of the previous stress algorithms, implementation required a special PROM set, which was configured separately from the three processor triple redundant controls, thereby incurring a significant additional cost. Furthermore, in the conventional systems, manual starting and loading instructions were determined based on stress calculations made remote from the turbine. Consequently, due to the inability to monitor the rotor surface metal stresses as they occur, the manual starting and loading instructions included very conservative ramp rates and hold times, thus wasting start-up time in operation. Additionally, conventional algorithms ran only about once every minute, which lead to a response time that is too slow for rapid steam and metal temperature changes as with combined cycle applications.
Rotor surface metal stress is proportional to the difference between surface metal temperature and average rotor temperature, and rotor bore (center) metal stress is proportional to the difference between average rotor and rotor bore temperatures. Conventionally, however, it has been difficult to rapidly determine accurate time lagged rotor bore temperatures and rotor average temperatures necessary for accurate and rapid thermal stress calculations.